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Thread: Logging Evohome Heat Demand

  1. #1
    Automated Home Guru
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    Default Logging Evohome Heat Demand

    Hi all,

    I have an original (v1) evohome with the RFG100 gateway. I have Domoticz set up (via web API) on a constantly-on computer and can log set points, room temperatures etc.

    I am wondering what is the easiest way for me to log which rooms are calling for heat demand. I understand this may only be possible by adding an HGI80, is that correct? Or would upgrading to the new Evohome WiFi model give this functionality?

    Thanks!

    Gareth

  2. #2
    Automated Home Guru
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    Dec 2016
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    Short answer:
    You need the HGI80 and even then I'm not sure whether this part of the protocol has been deciphered yet.

    Long answer:
    The web based protocol used by both the RFG100 and the Wifi controllers are strictly zone based, where a zone may contain multiple valves and one assigned temperature sensor. The web API does not support drilling into a zone to view its individual devices and thus is unable to report on whether there is a heat demand or not because this is not generated by the zone as a whole but by individual valves. This is actually rather tricky, because the Evohome system does have the option to allow local overrides by turning the dial on the HR92 but this does not override the zone as a whole - even if that HR92 is the only device in that zone. Therefore there is no way to tell for sure whether there is or should be a heat demand just by looking at the web API reports.

    Really the only way I can think of is to monitor the BDR91 itself, using either an optic sensor or a volt meter. Obviously this will just tell you that there is a heat demand, not which valve is generating it.

  3. #3
    Automated Home Legend paulockenden's Avatar
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    Default

    Domoticz with an HGI80 is able to show the heat demand per radiator, both as values and as a graph.

    chart.jpg

    chart (1).jpg

    P.

  4. #4
    Automated Home Guru
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    Feb 2016
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    Nice graphs Paul .

    PS I've recently added the OT Bridge to my Evohome set-up and been able to properly test out the Domoticz Evohome code for this device. I've made a small fix to the code to address an error in the heat demand processing for the OT Bridge which Bruce highlighted a long time ago. The fix should hopefully make it's way into the beta code in a couple of weeks. I'll post an update in a new thread once it's available.

  5. #5
    Automated Home Guru
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    Default

    Okay, so up until the fourth space in the short answer applies

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